In order to ascertain and manage states of targets which can freely move, senders or the like are mounted on the targets. For example, in order to manage domestic animals grazing in regions designated by fences or the like, senders or the like that have position detection functions are mounted on the domestic animals and positions of the domestic animals on which the senders are mounted are ascertained.
The following Patent Literature 1 discloses a technology for managing grazing of domestic animals by mounting identification tags with position detectors that acquire positional information using a global navigation satellite system (GNSS) on the domestic animals.